Utah State University DigitalCommons@USU All Graduate Theses and Dissertations Graduate Studies 5-1975 Nutritional Quality and Herbage Production of Intermediate Wheatgrass (Agropyron intermedium [Host] Beauv.) When Infested with Black Grass Bugs (Labops hesperius Uhler) Alan M. Gray Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Ecology and Evolutionary Biology Commons, Environmental Sciences Commons, Nutrition Commons, and the Plant Sciences Commons Recommended Citation Gray, Alan M., "Nutritional Quality and Herbage Production of Intermediate Wheatgrass (Agropyron intermedium [Host] Beauv.) When Infested with Black Grass Bugs (Labops hesperius Uhler)" (1975). All Graduate Theses and Dissertations. 6294. https://digitalcommons.usu.edu/etd/6294 This Thesis is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. NUTRITIONAL QUALITY AND HERBAGE PRODUCTION OF INTERMEDIATE WHEATGRASS (Agropyron intermedium [Host] Beauv.) WHEN INFESTED WITH BLACK GRASS BUGS (Labops hesperius Uhler) by Alan M. Gray A thesis submitted in partial fulfil !ment of the requirements for the degree of MASTER OF SCIENCE in Range Science Approved: UTAH STATE UNIVERSITY Logan, Utah 1975 ii ACKNOWLEDGEMENTS I extend my appreciation to Dr. John C. Malechek for his personal interest and guidance in my graduate program and for the technical assistance he provided on this project. I am also grateful for the contributions and reconnnendations of the following members of my Graduate Comnittee: Dr. Dale Bartos, Dr. B. Austin Haws, and Dr. Joseph Street. I am indebted to the following Utah stockmen who generously provided the project study areas: Mr. Gene Bertagnoly, Mr. Bud Carter, Mr. Vernal Carter, and Mr. Howard Mattsson. Thanks is also due to Mr. Kim Marshall fer his assistance with the statistical analysis of data. Finally, to my wife, Charlene for her encouragement and support in this endeavor, I am most grateful. Alan M. Gray iii TABLEOF CONTENTS Page ACKNOWLEDGMENTS. ii LIST OF TABLES. iv LIST OF FIGURES. v ABSTRACT.. vi INTRODUCTION 1 LITERATUREREVIEW .. 3 METHODSAND MATERIALS. 8 Study areas .•. 8 Experimental procedures 9 RESULTSAND DISCUSSION 14 Grass bug numbers 14 Herbage production. 16 Herbage dry matter content. 24 Crude protein content 29 Cell contents ... 33 SUMMARYAND CONCLUSIONS. 37 LITERATURECITED .... 41 iv LIST OF TABLES Table Page 1. Grass bug population numbers (mean± 95% C.I.) on two study sites . • • • . 14 2. Analysis of variance for herbage production on Site I . 16 3. Analysis of variance for herbage production on Site II. 20 4. Analysis of variance for seedhead production on Site I. • . • . • . 20 s. Analysis of variance for seedhead production at Site II . 23 6. Analysis of variance for percent dry matter in plants on Site I . 24 7. Analysis of variance for percent dry matter in plants on Site II. 29 8. Analysis of covariance for percent crude protein in plants on Site I. 29 9. Analysis of covariance for percent crude protein in plants at Site II . 32 10. Analysis of covariance for percent cellular contents in plants on Site I . 33 11. Analysis of covariance for percent cellular contents in plants at Site II. 33 v LIST OF FIGURES Figure Page L 1. hesperius: male (top), female (bottom) actual size 4 nun. • 4 2. Sweep method of sampling bug numbers. 12 3. D-Vac method of sampling bug numbers. 13 4. Forage production at Site I (kg/ha dry weight). 17 5. Forage production at Site II (kg/ha dry weight) 18 6. Seasonal production of seedheads at Site I (Nos. /m2) • • • • • • • • • • • • • • • • 21 7. Seasonal production of seedheads at Site II (Nos. /m2) • • • • • • • • • • • • • • • • 22 8. A. intermedium leaves from infested (left) and from control (right) plots at Site I. 25 9. A. intermedium leaves from infested (outside) and control (center) plots on Site II. 26 10. Percentage dry matter of herbage at Site I. 27 11. Percentage dry matter of herbage at Site II 28 12. Crude protein content of herbage at Site I. 30 13. Crude protein content of herbage at Site II 31 14. Percentage of cell contents of herbage at Site I. 34 15. Percentage of cell contents of herbage at Site II 35 vi ABSTRACT Nutritional Quality and Herbage Production of Intermediate Wheatgrass (Agropyron intermedium [Host] Beauv.) When Infested with Black Grass Bugs (Labops hesperius Uhler) by Alan M. Gray, Master of Science Utah State University, 1975 Major Professor: Dr. John C. Malechek Department: Range Science Two intermediate wheatgrass seedings with different levels of grass bug infestation were evaluated for herbage production, seedhead production, percent dry matter, crude protein, and cell contents. Study sites were located at different elevations on mountain summer ranges in northern (Site I) and central (Site II) Utah. Study plots at Site I and Site II were infested with 113 and 210 bugs per sweep, respectively. Herbage production appeared to be reduced in early spring on the site with the higher infestation; however, no effect on season-long herbage production could be detected on either site. Seed - head production on infested plots was reduced 45 percent at Site I and 56 percent at Site II. No important effect on dry matter content of infested plants was detected even though the leaves appeared to be dry and in a condition of moisture stress. Crude protein of infested plants was significantly higher (one to two percent) than control plants on the site with the higher infestation. The percentage of vii cell contents of plants on the more highly infested plot was eight percent less than the percentage of cell contents of control plants in the early spring. This reduction coincided with the period of peak damage. Later in the season this difference diminished as plant growth continued after the bug population completed its life cycle. (49 pages) INTRODUCTION In recent years the improvement and restoration of depleted range­ lands has often been accomplished by establishing grass monocultures. Because exotic cool season grasses have been highly productive in arid regions of the western United States, they have been used extensively to bring thousands of acres of depleted rangeland into a more stable condition by reducing erosion and increasing forage production for livestock. However, as often happens with broad-scale vegetation type conversions, complications have resulted and unforseen side­ effects of these practices have occurred. Pure stands of introduced wheatgrass, primarily crested wheatgrass (Agropyron cristatum (L.) Gaertn.) and intermediate wheatgrass (A. intermedium (Host) Beauv.), provide prime habitat for the development of large populations of black grass bugs (Labops hesperius Uhler). Stockrnen often become alarmed upon discovering a heavy infestation of grass bugs in critically-needed spring forage. Bug populations apparently require a number of growing seasons to build up to critical levels. Therefore, their presence is commonly discovered only after they have increased to levels that may inflict quite impressive visible damage. This apparent threat to forage production on seeded ranges has generated considerable interest but only limited research. Various speculations about the actual effect of Labops have been the result of numerous observations by many concerned individuals. 2 The objective of this study was to investigate the effects of Labops hesperius on forage nutritional quality and herbage production of intermediate wheatgrass, an introduced species which has been commonly used in range improvement programs. Indicators of forage nutritional quality in this study were considered to be percentage of crude protein and the percentage of cellular contents. These nutri­ tional attributes were thought important because they provide an indication of expected animal performance and are highly correlated to forage digestibility and intake by herbivores. Since crude protein is significantly correlated to digestible protein content, determination of the crude protein level of a plant can give a reasonably reliable indication of its feed value (Sullivan, 1962). The portion of plant dry matter consisting of cellular contents provides a collective indication of the presence of sugars, starch, and protein. 3 LITERATUREREVIEW Labops hesperius Uhler. (Figure 1) appears to be a native of the Intermountain Region. Labops is a true bug (Hemiptera:Miridae) and apparently causes only restricted or localized damage when present in climax native vegetation or floristically diverse connnunities. Prior to the introduction of new host species such as exotic wheatgrasses, Labops populations were probably restricted by native predators and other controlswithin the ecosystem. Labops hesperius was first reported as a new species as a result of an expedition into Montana by Dr. F. V. Hayden in 1871 (Uhler, 1872). Further works on the taxonomy and distribution of Labops spp. (Knight, 1922; Slater, 1954, 1954a) restricted its distribution to the northern halves of the eastern and western hemispheres, principally northwestern North America and northeastern Siberia. Extensive damage to introduced grasses by black grass bugs (Labops spp.) has been reported throughout the western United States (Bohning and Currier, 1967; Denning, 1948; Haws, Dwyer and Anderson, 1973; Knowlton, 1966; Pepper et